The present invention relates to a method and an apparatus for forming holograms for reproducing three-dimensional images.
Recent advances of computer-related techniques have made it possible to process three-dimensional image information easily. One popular means for outputting three-dimensional image information to be processed by a computer has been simulation of three-dimensional representation on a display. With such simulated three-dimensional representation, an image displayed on a display can be freely moved to allow three-dimensional observation of the displayed image. However, it is difficult to represent three-dimensional image information sufficiently using simulated three-dimensional representation because it is not a real representation of the three-dimensional image.
Means for outputting three-dimensional image information in practical use other than the above-described simulated three-dimensional representation include modeling apparatuses (also referred to as xe2x80x9csolid creatorsxe2x80x9d) which automatically create a model from three-dimensional image information. However, when three-dimensional image information is transmitted to a remote location such as a foreign country to evaluate it at that remote location using such a modeling apparatus, it is necessary to prepare the modeling apparatus at the remote location and to create a model actually using the modeling apparatus, which indicates that the use of such a modeling apparatus is not necessarily convenient output means in terms of cost and time. Especially, when three-dimensional image information is to be output in a plurality of locations, the method for outputting three-dimensional information using a modeling apparatus is impractical because it results in an enormous cost.
It is therefore desired to provide effective and practical means for outputting three-dimensional image information.
In the advertising and publishing industries, there is a need for creating advertisements or magazine front pages that give stronger impression. This has resulted in a need for simple three-dimensional image representation.
One possible technique for satisfying the above-described needs is to output three-dimensional image information utilizing holography. In general, the output of three-dimensional image information utilizing holography is performed by projecting reference light upon a recording medium in which an interference pattern is recorded as a result of interference between object light carrying image information and reference light, that is, a hologram.
However, the method of forming a hologram as a result of interference between object light and reference light allows only the recording of information of a real object and does not allow the recording of three-dimensional image information to be processed by a computer. Further, this method does not allow recording of information of even a real object if the object is too large. In addition, this method is unsuitable for people called creators who attempt to create images with characters such as titles and various visual effects added thereon. Moreover, it is difficult to form large holograms that can be used for advertisements on the street with this method.
There is a technique in prior art referred to as xe2x80x9ccomputer-synthesized holographyxe2x80x9d for forming holograms based on three-dimensional image information to be processed by a computer. According to this technique, for example, a computer calculates an interference pattern that should be generated as a result of interference between information light obtained by performing a Fourier transform on information of an object in a space to be three-dimensionally represented and reference light; the pattern is drawn with a normal printer or the like; the drawn pattern is photographed using a camera or the like to reduce it to a size which corresponds to the actual dimensions of the represented object and which is determined by the wavelength of the same; and a hologram is formed by printing the reduced pattern in the form of irregularities and dots.
However, the method for forming a hologram utilizing computer-synthesized holography according to the prior art is inadequate for the purpose of outputting three-dimensional image information to be processed by a computer easily because it involves many steps to be carried out. The method according to the prior art has another problem in that it is difficult to improve diffracting efficiency and the rendering capability of three-dimensional image representation because an interference pattern is recorded on a two-dimensional basis and, therefore, Bragg diffraction can not be effectively utilized.
Holographic printers for forming a hologram capable of representing a three-dimensional image are disclosed in Endoh et al., Recording of high resolution image by Holographic 3-D Printer, the 23rd Conference on Imaging Technology, pp. 317-320, 1992 and Yamaguchi et al., Holoprinter for three-dimensional image hardcopy, Journal of The Society of Electrophotography of Japan, Vol. 22, No. 4, pp-342-345, 1993.
In the case of those holographic printers, however, reference light for recording must correspond to reference light for reproduction because a two-dimensional image is displayed on a liquid crystal panel in association with an actual image displayed in a space and an interference pattern as a result of interference between light modulated by the two-dimensional image and reference light is recorded in a recording medium. This results in a problem in that it is difficult to create a variety of holograms for which different beams of reference light are used for reproduction.
The above-described holographic printers have another problem in that they have a complicated mechanism because there is a need for separated optical systems for illuminating a recording medium with light modulated by a two-dimensional image and for illuminating the recording medium with reference light.
The present invention has been conceived taking such problems into consideration, and it is a first object of the invention to provide an apparatus and a method for forming a hologram which make it possible to form a hologram for reproducing a three-dimensional image easily, free of limitations placed by the size of the three-dimensional image to be reproduced, the size of the hologram and reference light for reproduction.
In addition to the first object, it is a second object of the invention to provide an apparatus and a method for forming a hologram which make it possible to form a three-dimensional hologram.
In addition to the first object, it is a third object of the invention to provide an apparatus and a method for forming a hologram which make it possible to form a hologram with a simple mechanism.
A hologram forming apparatus according to the invention is a hologram forming apparatus for forming a hologram for reproducing a three-dimensional image by recording an interference pattern for generating reproduction light associated with a desired three-dimensional image when illuminated with reference light for reproduction in a recording medium on which information is recorded utilizing holography, the apparatus having a head for illuminating a part of the recording medium with a plurality of beams of recording light for forming a part of the interference pattern to record the part of the interference pattern and position change means for changing the relative positional relationship between the head and recording medium.
The hologram forming apparatus according to the invention forms a hologram by performing the operation of illuminating a part of a recording medium with a plurality of beams of recording light for forming a part of an interference pattern to record the part of the interference pattern using the head a plurality of times while changing the relative positional relationship between the head and recording medium with the position change means.
A method for forming a hologram according to the invention is a method for forming a hologram for reproducing a three-dimensional image by recording an interference pattern for generating reproduction light associated with a desired three-dimensional image when illuminated with reference light for reproduction in a recording medium in which information is recorded utilizing holography, in which an operation of illuminating a part of the recording medium with a plurality of beams of recording light for forming a part of the interference pattern to record the part of the interference pattern is performed a plurality of times while changing the relative positional relationship between the recording medium and the beams of recording light.
Other objects, features and advantages of the invention will become sufficiently apparent from the following description.